Heavy Mn²⁺ Doped MgAl₂O₄ Phosphor for High‐Efficient Near‐Infrared Light‐Emitting Diode and the Night‐Vision Application

Abstract Photoluminescence originated from doped activators in the solid state materials usually faces the challenge of concentration quenching, restricting the further increase of photoluminescence intensity. Herein, a new strategy is demonstrated by the heavy doping Mn²⁺ into MgAl₂O₄, leading to the broad‐band near‐infrared (NIR) emission peaking at ≈825 nm with a full width at half maximum of ≈125 nm, as well as high internal quantum efficiency of ≈53% upon 450 nm laser excitation. Density functional theory calculation and extend X‐ray absorption fine structure provide a understanding of Al³⁺/Mn²⁺ disorder and Mn²⁺–Mn²⁺ aggregation in spinel Mg_1–xAl₂O₄:xMn²⁺ with high Mn²⁺ content, which enables the formation of superexchange coupled ^IVMn²⁺–^VIMn²⁺ pair. The NIR light‐emitting diodes fabricated by the 450 nm blue chip and Mg_0.50Al₂O₄:0.50Mn²⁺ phosphor gives a high NIR output power of ≈78.41 mW under a driven current of 120 mA, and night‐vision application as light source in the dark is demonstrated. This work opens new paths for rational design of efficient broad‐band NIR emitting phosphor, and also provides new insights into the Mn²⁺ luminescence and the applications.